Degradation behaviours

2 Late twentieth and early twenty-first century fibres 

14 Comparative ATR spectra of soya bean protein fibres and natural and synthetic fibres. Textile Conservation Centre, University of Southampton. 

The durability of organic materials exposed to the outdoor environment is determined to a large extent by incident solar radiation. While other weather factors contribute to limiting the lifetime of a material exposed to outdoor conditions, the absorbed solar energy is mainly responsible for the 

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Presence of nanosilica and its interaction with the rubber matrices strongly affect the low and high temperature degradation behaviour of the hybrid nanocomposites. Figure 3.24 shows the post-aging swelling analysis of the cross-linked ACM-sihca and ENR-silica hybrid nanocomposites. The data points are collected after aging of the samples at 50°C, 70°C, and 90°C for 72 h. 

As discussed earlier under Section 2.3, Carbonyl index, in one relatively recent comparison of the photo-oxidative and thermal (oven-aged) degradation behaviour of different polyethylenes, additive free grades of a metallocene (mPE), an HDPE and a linear low-density PE (LLDPE) were analysed by a combination of mid-IR spectroscopy, TGA and CL [13]. The mid-IR... 

A study was made of the thermal degradation behaviour of PS foams used as patterns in the lost foam process for metal casting. The data indicated that the thermal degradation of the pattern had a strong effect on mould filling and casting quality. The use of other types of foam such as PE, PP, PMMA and styrene-methyl methacrylate copolymers to overcome problems encountered with PS foam patterns is discussed. 7 refs. 

Secondly For long-term applications not only the softening point is of importance, but also the degradation behaviour of the polymer it may quite well happen that the polymer suffers unallowable degradation considerably below its softening T (see MT 8.1.5)... 

Gomes, M. E., Ribeiro, A. S., Malafaya, R. B., Reis, R. L., Cunha, A. M. (2001). A new approach based on injection moulding to produce biodegradable starch based polymeric scaffolds Morphology, mechanical, and degradation behaviour. Biomaterials., 22, 883-889. 

Transparent hydrogels useful for adhesion inhibitors, tissue adhesives, wound dressings, hemostatics and embolisation materials are obtained from dextran methacrylates via polymerisation with N-isopropylacrylamide in DMSO in the presence of azobisisobutyronitrile [176]. A broad variety of new hydrogels with different sensitivities and tunable degradation behaviour is accessible by grafting L-lactide onto 2-hydroxyethyl methacrylate (HEMA) and binding this polymerisable group on dextran via activation with N,N -carbonyldiimidazole (CDI, Sect. 4.2.2) [177]. 

B.N. Jang, M. Costache, and C.A. Wilkie, The relationship between thermal degradation behaviour of polymer and the fire retardancy of polymer/clay composites, Polymer, 2005, 46 10678-10687. 

McNeill, I.C. and Mohammed, M.H., A comparison of the thermal degradation behaviour of ethylene-ethyl acrylate copolymer, low density polyethylene and poly(ethyl acrylate), Polym. Deg. Stab., 1995,48, 175-187. 

Chemical structures, thermal degradation behaviour and light absorption spectra are shown for ethyl-2-cyano-3,3-diphenylacrylate (Uvinul 3035), 2-ethylhexyl-2-cyano-... 

Although it is reasonable to expect differences in degradation behaviour between random and heterophase copolymers, literature seldom defines clearly the nature of copolymers studied. Well characterized heterophase E-P copolymers, however, are of very recent origin. 

Jun, J., Jun, J., Kim, K. (2002). Degradation behaviour of Al-Fe coatings in wet-seal area of molten carbonate fuel cells. J. Power Sources 112,153-161. 

Blanco MD. Sastre RL, Teijon C, et al. Degradation behaviour of microspheres prepared by spray-drying polyCD. L-lactide) and poly(D, L-lactide-co-glycolide) polymers. Int J Pharm 2006 326 139 7. 

Turton, T.J. White, J.R. Observation of different photo-degradation behaviour in two similar polypropylenes. J. Mater. Sci. 2001, 36, 4617-4624. 

Polymer degradation can be analysed at macroscopic, macromolecular or molecular scale. Fig. 2. The detection of early degradation and small differences in degradation behaviour between different materials requires an... 

The degradation behaviour in this case cannot be obtained from the preceding equations, which are restricted to first-order termination or second-order disproportionation termination. Another method [2] restricted to a most probable type initial distribution has shown that in this case, in the absence of transfer... 

The degradation behaviour of polymethylmethacrylate is easily characterized by thermal volatilization analysis [87] (Fig. 29). Monomer is obtained in very high yield in all cases. A polymer sample prepared by a free radical reaction undergoes a rapid depolymerization at about 275°C as indicated by the first peak. The second peak, situated between 350 and 400°C, corresponds to a second mode of initiation of chain depolymerization. For samples prepared by anionic polymerization, the first peak is not observed. Depolymerization of the whole sample occurs above 350°C. 

Differences in the degradation behaviour of polymers in solution as a function of LET has indeed been observed by Henglein and co-workers. The results obtained for various polymers are summarized in Table 35 [442]. The more efficient radiation has been underlined in the cases where the effects of high and low LET are qualitatively the same. For the dilute solutions ( 1%), the more efficient radiation is Li—He in only one... 

Walter, R., Mehjabeen, A., Gordon, T. and Kannan, M.B. (2013) Precipitation of Struvite on Pure Magnesium and in vitro Degradation Behaviour, In Proc., CHEMECA 2013 Challenging Tomorrow, 29 September - 2 October 2013, Brisbane, QLD, Australia, 909 -912. 

Kim TN, Feng QL, Kim JO, Wu J, Wang H, Chen GC, Cui FZ (1998) Antimicrobial effects of metal ions (Ag, Cu, Zn ) in hydroxylapatite. J Mater Sci Mater in Med 9 129-134 Klein CP AT, Driessen AA, de Groot K (1984) Relationship between the degradation behaviour of calcium phosphate ceramics and their physical chemical characteristics and trltrastractrrral geometry. Biomaterials 5 157-160... 

Thus far, the behaviour of the nitrogen atoms of the corresponding redox states in PPY and PAN towards oxidation, reduction, protonation and CT interactions has been found to be very similar. However, the nitrogen atoms of the two oxidized polymer complexes do differ in their thermal degradation behaviour which suggests that the oxidized pyrrolylium nitrogen atoms are more susceptible to de-protonation than their protonated EM base counterparts [105] (see Section 3.4). Furthermore, the amine nitrogen atoms in the EM oxidation state of PAN arc more susceptible to protonation in the presence of excess protonic acids than those of the DP-PPY [106]. Recent studies [204]... 

The similarities in the manner in which PPY and PAN undergo protonation/dc-protonation oxidation/reduc-tion and CT interactions have been described in Section 3.2, However, the nitrogen atoms of the two oxidized polymer complexes differ in thermal degradation behaviour [105], As mentioned before, the PPY/ chloride complex degrades via a de-protonation process as suggested by the loss of the chloride species and by the appearance of the de-protonated pyrrolylium... 

Through a comprehensive review of the recent conductive polymer literature, it has been demonstrated that photoelectron spectroscopy provides a very unique and powerful tool for analyzing the intrinsic structure, the charge transfer interaction, and the stability and degradation behaviour of electroactive polymers. It is further demonstrated that photoelectron spectroscopy is also ideal for investigating the chemistry and electronic structure of the electroactive polymer interface with other polymers, semi-conductors, and metals. The surface and interfacial analytical capability of photoelectron spectroscopy can be further extended to include molecular specificity when coupled with the SIMS technique. Finally, the imaging XPS technique is fast becoming widely available [368]. 

As the conductive polymers are similar to various other materials such as amorphous polymers, inorganic intercalates, semiconductors, solid electrolytes and metals in one way or the other and these materials show wide range of degradation kinetics in different environments as well as dependence on temperature and the composition of the material. Hence, the predictions about degradation behaviour seem to be risky without experimental data. Also, one has to be very careful in extrapolating the available data which may lead to erroneous results. 

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